Hi @LuisC ,
Thank you for your interest in the NXP MIMXRT product, I would like to provide service for you.
I already help you to check with our MCUBootutility author, who is also the flashloader expert.
The answer is: MCUbootutility just support the FSPI1 primary group and FSPI2 primary group, no FSPI1 second group and FSPI2 second group now, but RT1170 chip can support it, just the tool still didn't support it.
If you want to download the code to the secondary group nand, you need to modify the flashloader code to let the flashloader download code to the secondary group for the nand. If you want to boot from the flexspi nand secondary group, you also need to burn the fuse:

Wish it helps you!
If you still have questions about it, please kindly let me know.
Best Regards,
Kerry